Method and apparatus for determining writing power for recording data

ABSTRACT

A method and apparatus for determining an optimal writing power for recording data on a recording medium such as an optical disk, are discussed. The method according to an aspect of the present invention includes (a) performing an optimal power calibration (OPC) operation on a first area of the recording medium, and detecting a first writing power based on the OPC operation performed on the first area; (b) performing an OPC operation on a second area of the recording medium after erasing data on the second area, and detecting a second writing power based on the OPC operation performed on the second area; and (c) determining an optimal writing power for recording data on the recording medium based on the detected first and second writing powers.

This application claims priority to the Korean Patent Application No.10-2005-0095287, filed in Korea on Oct. 11, 2005, which is herebyincorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus for determiningoptical writing power for recording data on a recording medium such asan optical disk.

2. Description of the Related Art

FIG. 1 shows areas allocated in a CD-RW disk with emphasis on the PCA(power calibration area) used for determining optical writing power. Ageneral optical disk recording apparatus performs an OPC (optimal powercalibration) operation on the PCA of an optical disk to determine awriting power optimal for the optical disk recording apparatus and theoptical disk before actually recording data in the program area of theoptical disk.

As shown in FIG. 1, the OPC operation records test data of apredetermined length in the test area of the PCA several times withvarying writing powers and reproduces the recorded test data todetermine the writing power which results in the best-quality signalswhen the test data is reproduced, thereby determining the optimalwriting power. The test area in, the PCA is organized into 100partitions, each of which can accommodate 15 ATIP frames. Each OPCoperation records 15 frames in one of the 100 partitions. The 15 framesare recorded with 15 different writing powers.

Because the PCA is organized into 100 partitions, the optical disk canallow up to 100 new OPC operations. In other words, the first 100 OPCoperations are performed in partitions wherein no data has been recordedbefore.

After each test recording is completed, null data of a size of one frameis written in the count area of the PCA to indicate that 1 OPC operationis conducted.

If the optimal writing power is determined after the OPC operation, data(i.e., not the test data) is recorded in the program area (data area) ofthe optical disk with the determined optimal writing power afterwards.

It is common that a rewritable optical disk is used in such a way thatdata recorded in the data area of the optical disk can be overwrittenwith new data if the old data is not necessary. According to thispractice, when the old data recorded in a particular area of the dataarea is overwritten with the new data, the old data is DC erased firstbefore the new data is recorded in the same data area. But, the qualityof the recording layer of the rewritable disk is deteriorated with therepeated DC erasing and data recording operations. Therefore, theproperty of the rewritable optical disk at the moment of a first datarecording in a data area is different from that at the moment of theoverwrite in the data area. As a result, it is desirable that thewriting power for overwriting the old data be different from the writingpower determined at the initial data recording even for the samelocation of the optical disk.

According to the related art, however, when overwriting of data isperformed in a data area of an optical disc, the OPC operation fordetermining an optimal writing power in that data area is performed inthe test area of the PCA wherein no test data has been recorded before,if the number of data recording operations conducted thus far is lessthan 100. Thus the writing power determined in such a way leads to thedeterioration of recording quality because the determined writing poweris not suitable for data areas wherein DC erasing operations have beenperformed repeatedly.

SUMMARY OF THE INVENTION

In view of the above and other problems associated with the related art,it is an object of the present invention to provide a method andapparatus for determining an optimal writing power for recording data ona recording medium in consideration of the deterioration of the qualityof the recording medium caused by repeated data recording and dataerasing operations.

Another object of the present invention is to provide a recordingmedium, method and apparatus for determining an optimal writing power,which address the limitations and disadvantages associated with therelated art.

A method for determining an optimal writing power in accordance with oneembodiment of the invention detects a first writing power by performingan OPC operation for a first area of a recording medium, detects asecond writing power by performing an OPC operation for a second area ofthe recording medium after erasing data in the second area and, anddetermines the writing power for recording data based on the detectedfirst and second writing powers.

In one embodiment of the invention, the power calibration area (PCA) ofthe recording medium is divided into two sub-areas of the same size andan OPC operation is performed in an arbitrary section of one of thesub-areas after a DC erasing operation.

In one embodiment of the invention, if a request for writing data is therequest for a data overwrite, the second writing power is detected andused for determining the wring power for recording data.

In one embodiment of the invention, the average of the first writingpower and the second writing power is used as the writing power.

According an aspect of the present invention, there is provided a methodfor determining an optical writing power for recording data on arecording medium, the method comprising: (a) performing an optimal powercalibration (OPC) operation on a first area of the recording medium, anddetecting a first writing power based on the OPC operation performed onthe first area; (b) performing an OPC operation on a second area of therecording medium after erasing data on the second area, and detecting asecond writing power based on the OPC operation performed on the secondarea; and (c) determining an optimal writing power for recording data onthe recording medium based on the detected first and second writingpowers.

According another aspect of the present invention, there is provided amethod for recording data on a recording medium, the method comprising:(a) moving to an always-overwrite optimal power calibration (AOPC) areawithin a test area allocated in the recording medium; (b) DC-erasing theAOPC area; (c) detecting a writing power by performing an OPC operationon the DC-erased AOPC area, and determining an optimal writing power forrecording data based on at least the detected writing power; and (d)writing data in a data area of the recording medium using the determinedoptimal writing power.

According another aspect of the present invention, there is provided amethod for determining an optical writing power for recording data on arecording medium, the method comprising: (a) performing a plurality ofOPC operations on a particular area of the recording medium, theplurality of OPC operations being performed in mutually differentmanners; and (b) determining an optimal writing power for recording dataon the recording medium based on writing powers detected from theplurality of OPC operations.

According another aspect of the present invention, there is provided anapparatus for recording and/or reproducing data on a recording medium,comprising: a recording/reproducing unit configured to record signals onthe recording medium and/or to reproduce signals from the recordingmedium; a servo unit configured to control position of a laser beamirradiated onto the recording medium by the recording/reproducing unit;and a controller configured to control the recording unit/reproducingunit and the servo unit to record signals in an arbitrary position onthe recording medium and/or to reproduce or erase signals recorded in anarbitrary position on the recording medium, wherein the controllerperforms an optimal power calibration (OPC) operation on a first area ofthe recording medium, performs an OPC operation on a second area of therecording medium after erasing data on the second area, detects firstand second writing powers respectively from the OPC operations performedon the first and second areas, and determines an optimal writing powerfor recording data based on the detected first and second writingpowers.

According another aspect of the present invention, there is provided anapparatus for recording data on a recording medium, comprising: arecording unit configured to record signals on the recording medium; aservo unit configured to control a position of a laser beam irradiatedonto the recording medium by the recording unit; and a controllerconfigured to control the recording unit and the servo unit to recordsignals in an arbitrary position on the recording medium, wherein thecontroller performs a plurality of OPC operations on a particular areaof the recording medium, the plurality of OPC operations being performedin mutually different manners, and determines an optimal writing powerfor recording data on the recording medium based on at least writingpowers detected from the plurality of OPC operations.

According another aspect of the present invention, there is provided anapparatus for recording data on a recording medium, comprising: arecording unit configured to record signals on the recording medium; aservo unit configured to control a position of a laser beam irradiatedonto the recording medium by the recording unit; and a controllerconfigured to control the recording unit and the servo unit to recordsignals in an arbitrary position on the recording medium, wherein thecontroller contains division information for dividing a test area of therecording medium and performs a plurality of optimal power calibration(OPC) operations on the divided test area according to the divisioninformation.

These and other objects of the present application will become morereadily apparent from the detailed description given hereinafter.However, it should be understood that the detailed description andspecific examples, while indicating preferred embodiments of theinvention, are given by way of illustration only, since various changesand modifications within the spirit and scope of the invention willbecome apparent to those skilled in the art from this detaileddescription.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention, illustrate the preferred embodiments ofthe invention, and together with the description, serve to explain theprinciples of the present invention.

In the drawings:

FIG. 1 illustrates areas allocated in a CD-RW disk with emphasis on thePCA (power calibration area) used for determining an optimal writingpower according to a related art;

FIG. 2 illustrates a block diagram of an optical diskrecording/reproducing apparatus embodying the present invention;

FIG. 3 illustrates an example in which the test area of the PCA isdivided into two sub-areas for determining an optimal writing power inaccordance with one embodiment of the invention; and

FIG. 4 illustrates a flow chart of a method for determining an optimalwriting power using divided test areas for performing OPC operations inaccordance with one embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In order that the invention may be fully understood, preferredembodiments thereof will now be described with reference to theaccompanying drawings.

FIG. 2 is a block diagram of an optical disk recording/reproducingapparatus embodying the present invention.

Referring to FIG. 2, the apparatus comprises a first digital signalprocessor (DSP) 30 a for recording, which converts input digital datainto a recording format by adding ECC, etc, a channel bit encoder 40 forconverting the data in the recording format from the first DSP 30 a intoa bit stream, an optical driver 41 for generating an optical drivesignal according to the bit stream, an optical pickup 20 for recordingthe bit stream on an optical disk 10 by irradiating a laser beamaccording to the optical drive signal onto the optical disk 10 and fordetecting signals recorded on the optical disk 10 from the reflectedlaser beam, an R/F unit 50 for generating a binary signal andfocus/tracking error signals from the signals detected by the opticalpickup 20, a drive unit 60 for driving a spindle motor 11 for rotatingthe optical disk 10 and for driving a sled motor 21 for moving theoptical pickup 20, a servo unit 61 for controlling the drive unit 60based on the focus/tracking error signals and the rotational speed ofthe optical disk 10, a second digital signal processor (DSP) 30 b forreproduction, which retrieves original digital data from the binarysignal using a clock synchronized with the binary data, a memory (e.g.,EEPROM) 71 for storing values of target β, target γ, and target powerassociated with each of disk manufacturers (disk codes) and recordingspeeds, and any other information, and a microprocessor 70 forperforming the OPC operation in a specified area of the optical disk 10and for controlling all the components as needed so that requestedrecording operations can be performed using the detected optimal writingpower. The microprocessor 70 also controls other operations of theapparatus. All the components of the apparatus are operatively coupledand configured.

FIG. 3 shows an example wherein the microprocessor 70 utilizes a testarea 300 of a PCA of an optical disc 10 by dividing the test area inaccordance with an embodiment of the present invention. The PCA includesthe test area 300 and a count area 310. In this example, the test area300 of the PCA of the optical disk 10 is divided into OPC_A and OPC_Bareas.

In one embodiment of the invention, the test area of the PCA is dividedinto OPC_A area and OPC_B area of the same size. In general, the testarea is from Ts1-00:15:05 to Ts1:00:35:65, wherein Ts1 indicates thetime information on the start position 301 of the lead-in area of thedisk 10. Therefore, OPC_A area is from Ts1-00:15:05 to Ts1-00:25:35 andOPC_B area is from Ts1-00:25:35 to Ts1-00:35:65. The count area is fromTs1-00:13:25 to Ts1-00:15:05.

The microprocessor 70 of the optical disk recording apparatus in FIG. 2recognizes the test area 300 of the optical disk 10 as two dividedareas. The information on the position that divides the test area isstored in the memory 71 or hard-coded into the program which themicroprocessor 70 executes. Though the test area 300 is divided into twoareas of the same size in one embodiment of the invention, the test area300 may be divided into any number of sub-areas of the same or differentsizes if necessary. Such case is also considered to fall within thescope of the invention if a DC erasing is executed in one sub-areabefore an OPC operation is executed.

In one embodiment of the invention, each OPC operation executed in OPC_Barea is always preceded by a DC erasing, whereas a conventional OPCoperation is performed in OPC_A area.

The test area according to the related art can accommodate up to 100 OPCoperations in areas wherein no data has been recorded before. In thepresent invention, however, the test area 300 is divided into OPC_A areaand OPC_B area of the same size and therefore up to 50 OPC operationscan be performed in unwritten partitions of OPC_A area. After the first50 OPC operations are executed, a DC erasing is required to perform thenext OPC operations in OPC_A area.

On the other hand, when an OPC operation is to be performed in OPC_Barea, a DC erasing is always executed before each of the actual OPCoperations is performed, so as to return the OPC_B area to the blankstate. Then the actual OPC operation is performed in a partition inOPC_B area, the partition being randomly selected from 50 partitions inOPC_B area.

According to an embodiment, two separate OPC operations may be performedrespectively in OPC_A and OPC_B areas. However, 1-frame null data iswritten in the count area 310 each time an OPC operation is performed inOPC_A area. The number of OPC operations executed in OPC_A area can beobtained based on the length of null data written in the count area 310.If the number reaches the maximum number of OPC operations which can beexecuted in OPC_A area (e.g., 50), OPC_A area is DC erased so thatfurther OPC operations can be performed in OPC_A area.

FIG. 4 shows a flow chart of a method for determining an optical writingpower in accordance with one embodiment of the invention, which will bedescribed in detail with reference to FIGS. 2 and 3. This method isimplemented by the apparatus of FIG. 2, but can be implemented by othersuitable device/system.

Referring FIG. 4, if the optical disk 10 is loaded in the apparatus ofFIG. 2, the microprocessor 70 performs predetermined basic operationssuch as disk type detection and servo initialization. If data recordingis requested (S10), the microprocessor 70 obtains the number of OPCoperations previously performed from the length of null data written inthe count area 310 of the optical disk 10 to determine where to performthe next OPC operation in OPC_A area. If the obtained number of theperformed OPC operations is N, the next OPC operation is performed at alocation at a distance of 15×(N+1) ATIP frames inward from the startposition of OPC_A (Ts1-00:15:05).

The location in which the next OPC operation will be performed may bedetected in a different manner. The microprocessor 70 first moves theoptical pickup 20 to the start position of OPC_A area (Ts1-00:15:05) andcontrols the optical pickup 20 to move inwardly, i.e., towards the innerareas of the disk 10. As the optical pickup 20 moves inward, a signalindicating whether the laser beam spot is on an unwritten area isgenerated by the RF unit 50. This signal is called ‘RECD’ wherein thestate of this signal is ‘L’ if the current location is an unwritten areaor is ‘H’ otherwise. Monitoring the ‘RECD’, the microprocessor 70detects the position wherein the ‘RECD’ switches from ‘H’ to ‘L’ andperforms the next OPC operation at a location which is at a distance of15 ATIP frames inward from the detected position.

If the location in which the next OPC operation will be performed isdetermined, the OPC operation will be performed from the determinedlocation as follows.

The microprocessor 70 reads the target power corresponding to the codeof the optical disk 10 and OPC writing speed from the memory 71, andprovides a writing power adjustment signal for changing the writingpower by a predetermined step from the detected target power each timefor the optical driver 41.

The optical driver 41, responsive to the writing power adjustmentsignal, outputs signals for writing the test data with the optical powercorresponding to the writing power adjustment signal. The optical pickup20 starts recording the signals for writing the test data, which areprovided by the optical driver 41, from the determined location. Asdescribed before, one OPC operation writes 15 frames with 15 differentwriting powers.

After completing the recording of the test data, the microprocessor 70controls the optical pickup 20 to reproduce the recorded test data anddetects the quality of the reproduced test data. If the optical disk 10is a one time writable disk (e.g., CD-R), the microprocessor 70 detectsthe β value from the reproduced RF signal, the β value indicating thedegree of asymmetry of the reproduced RF signal. Using the β value andthe writing power Pw which yields the β value associated with each ofthe 15 writing powers, the microprocessor 70 obtains a curve fit of thevalues (β, Pw). The microprocessor 70 determines the optimal writingpower for OPC_A area based on the obtained curve fit, the code of theoptical disk 10, and the target β value stored in the memory 71 (S11).

If the optical disk 10 is a rewritable disk, the microprocessor 70obtains the modulation index γ, which indicates the amplitude of the RFsignal reproduced from the recorded test data, instead of the β value.The microprocessor 70 detects the value of γ associated with eachwriting power and determines the optimal writing power for OPC_A areabased on the values of γ.

After the OPC operation in OPC_A area is completed, the microprocessor70 writes 1-frame null data in the count area 310 of the optical disk 10as described before.

If the OPC operation is completed at step S10, the microprocessor 70determines whether the request for writing data (e.g., in a data area ofthe disk 10) is the request for an overwrite operation (S20). If not,i.e., data is to be written in an unwritten area (e.g., in an unwrittenarea of the data area), the microprocessor 70 performs the requestedwriting operation in the unwritten part of the data area (e.g., programarea, etc.) of the optical disk 10 using the optimal writing powerdetermined at step S11 (S21 and S22).

The decision on whether the writing operation on the data area of thedisk is a data overwrite can be made based on the existence of recordeddata at the location wherein the recording is to be done. The existenceof recorded data can be examined from the information on the recordingsections of each track written in the PMA. If the location wherein therecording is to be done belongs to a section of a track written in thePMA, it is determined that the requested recording operation is a dataoverwrite.

If it is determined at step S20 that the requested recording operationis an overwrite of data in the data area of the optical disk 10, themicroprocessor 70 performs an additional OPC operation in OPC_B areaafter finishing the OPC operation in OPC_A area. The microprocessor 70first DC-erases OPC_B area and moves the objective lens of the opticalpickup 20 to an arbitrary position, and performs the aforementioned OPCoperation to determine an optimal writing power for OPC_B area (S30).Alternatively, the microprocessor 70 selects a location in OPC_B areaand performs the aforementioned OPC operation after DC-erasing of atleast 1 partition in OPC_B area from the location.

The reason for performing the OPC operation in OPC_B area afterDC-erasing OPC_B area in the case of a data overwrite is to make thecondition under which the optimal writing power is to be determinedsimilar to the condition under which data is to be actually written inthe data area of the optical disk 10 after the DC erasing. This allowsthe optimal writing power determined from OPC_B area to be more suitablefor the data overwriting operation in the data area.

If the two optimal writing powers are obtained by performing two OPCoperations in OPC_A and OPC_B areas, respectively as discussed above,the microprocessor 70 fixes the average of the two determined optimalwriting powers (from OPC_A and OPC_B areas) as the optimal writing powerfor the current disk. Once the optimal writing power is determined, themicroprocessor 70 performs the requested data recording (e.g., dataoverwriting) in the data area of the optical disk 10 with the determinedoptimal writing power (S32). As an alternative, if a data overwriting isrequested in a data area, then the optimal writing power determined onlyfrom OPC_B area after the DC-erasing, may be used as the optimal writingpower for the disk in the data overwriting operation.

In the embodiment shown in FIG. 3, if the requested recording operationis a data overwrite, the average of the two writing powers obtained fromOPC_A and OPC_B areas is adopted as the optimal writing power. This isbecause though N−1 overwrites were performed in the data area of theoptical disk 10, it is quite likely that the number of overwritesoperations conducted in the area in which the N-th overwrite will bedone is not N−1, considering that data is not always recorded in all ofthe data area of the optical disk 10. But (N−1) DC erasing operationswere actually executed in OPC_B area.

In other words, the number of overwrite operations conducted in the areain which a data overwrite is to be done is likely to be less than N−1.As a result, the average of the writing power detected in OPC_A areawherein a DC erasing is rarely executed (1 DC erasing is executed after50 write operations in the previous embodiment) and the writing powerdetected in OPC_B area wherein a DC erasing is executed at everyoverwrite operation is preferably adopted as the optimal writing power.

As a variation, instead of using the average of the optimal writingpowers determined from OPC_A and OPC_B area, a weighted sum obtained byadding such two products ((a1×writing power from OPC_A)+(a2×writingpower from OPC_B)) can be used as the optimal writing power, wherein a1and a2 are constants. Here, the sum of the constants a1 and a2 is 1,each of the constants a1 and a2 being less than 1. The constants a1 anda2 can be determined in consideration for the ratio of the averageamount of data recorded by a single writing operation to the capacity ofthe optical disk 10. For example, if the average amount of data recordedby a single writing operation is ¼ of the disk capacity, it is expectedthat one DC erasure is conducted in every 4 writing operations. In thiscase, it is desirable to set a1 to 0.25 and a2 to 0.75. Other examplesare possible.

Manufacturers of optical disks, therefore, may investigate the averageamount of data recorded in each writing operation and determine thevalues of a1 and a2 depending on the average amount of data. The valuesof a1 and a2 can be stored in the memory 71 or hard-coded into theprogram executed by the microprocessor 70, and can be used to determinethe optimal writing power.

It is also possible to let the user of the optical disk recordingapparatus adjust the values of a1 and a2 for determining the optimalwriting power. For example, the optical disk recording apparatus mayprovide a message like “The frequency of data overwrites is high,medium, or low?” to the user, e.g., on the associated screen, anddetermines the values of a1 and a2 depending on the user's response. Ifthe frequency is selected to be high, the value of a1 can be selected tobe higher than 0.5, wherein a1+a2=1. If the frequency is low, the valueof a1 can be selected to be lower than 0.5, wherein a1+a2=1. The numberof frequency intervals for determining the values of a1 and a2 can beincreased for more delicate adjustment.

At least one embodiment of the method for determining an optimal writingpower in accordance with the present invention can improve the qualityof recorded signals by determining an optimal writing power for a dataoverwrite operation and performing the data overwrite operation with thedetermined optimal writing power. The advantages and benefits of thepresent invention over conventional methods become larger as the numberof overwrite operations to be performed on an optical disk increases.

While the invention has been disclosed with respect to a limited numberof embodiments, those skilled in the art, having the benefit of thisdisclosure, will appreciate numerous modifications and variationstherefrom. It is intended that all such modifications and variationsfall within the spirit and scope of the invention.

1. A method for determining an optical writing power for recording dataon a recording medium, the method comprising: (a) performing an optimalpower calibration (OPC) operation on a first area of the recordingmedium, and detecting a first writing power based on the OPC operationperformed on the first area; (b) performing an OPC operation on a secondarea of the recording medium after erasing data on the second area, anddetecting a second writing power based on the OPC operation performed onthe second area; and (c) determining an optimal writing power forrecording data on the recording medium based on the detected first andsecond writing powers, wherein the first area and second area are areasof a test area within a power calibration area (PCA) allocated in therecording medium.
 2. The method of claim 1, wherein the steps (b) and(c) are executed when a request for writing data on the recording mediumis a data overwriting request.
 3. The method of claim 1, wherein thestep (b) performs the OPC operation on the second area, afterarbitrarily selecting a predetermined section from the second area whosedata is erased.
 4. The method of claim 1, further comprising: (d)writing data of a predetermined length in a count area allocated in therecording medium to indicate that the number of OPC operations performedon the recording medium is incremented by 1 after performing the OPCoperation on the first area.
 5. The method of claim 1, furthercomprising: (d) writing recording-requested data in a data area of therecording medium with the determined optimal writing power.
 6. Themethod of claim 1, wherein in the step (c), the optimal writing power isdetermined by multiplying the first writing power by a constant a1 andmultiplying the second writing power by a constant a2 and then addingthe two products, where a1<1, a2<1, and a1+a2=1.
 7. The method of claim6, wherein each of the constants a1 and a2 equals 0.5.
 8. An apparatusfor recording and/or reproducing data on a recording medium, comprising:a recording/reproducing unit configured to record signals on therecording medium and/or to reproduce signals from the recording medium;a servo unit configured to control position of a laser beam irradiatedonto the recording medium by the recording/reproducing unit; and acontroller configured to control the recording unit/reproducing unit andthe servo unit to record signals in an arbitrary position on therecording medium and/or to reproduce or erase signals recorded in anarbitrary position on the recording medium, wherein the controllerperforms an optimal power calibration (OPC) operation on a first area ofthe recording medium, performs an OPC operation on a second area of therecording medium after erasing data on the second area, detects firstand second writing powers respectively from the OPC operations performedon the first and second areas, and determines an optimal writing powerfor recording data based on the detected first and second writing powerspowers, wherein the first area and second area are areas of a test areawithin a power calibration area (PCA) allocated in the recording medium.9. The apparatus of claim 8, wherein the controller performs an OPCoperation after arbitrarily selecting a predetermined section from thesecond area whose data is erased.
 10. The apparatus of claim 8, whereinthe controller adopts a value, obtained by multiplying the first writingpower by a constant a1 and multiplying the second writing power by aconstant a2 and then adding the two products, as the optimal writingpower, where a1<1, a2<1, and a1+a2=1.